Metal working

ABSTRACT

This invention involves a process and apparatus for deforming metal which consists of applying pressure to the metal surface of a magnitude to effect preselected directional metal flow. The pressure is applied in the form of dual working forces superimposed on one another. One of the working forces consists of a relatively steady continuous force while the other is pulsating. A preferred apparatus of the present invention consists of a die axially mounted relative to an elongated workpiece and free to move a limited distance along this axis. Parallel dual working means, one being disposed to provide a relatively steady working force and one being disposed to provide a pulsating working force are mounted to drive said die over said workpiece or said workpiece through said die. Other embodiments of the present invention include an apparatus and method for stamping and deep drawing sheet or strip metal with a die by utilizing parallel dual steady and pulsating working forces.

United States Patent [72] inventors John Wesley l'llnshaw Garden Grove; William Clyde Dobeney, Torrance, both of, Calif. [21] Appl. No. 737,062 [22] Filed June 14, 1968 [45] Patented June 22, 1971 [73] Assignee The Battelle Development Corporation Columbus, Ohio [54] METAL WORKING 17 Claims, 12 Drawing Figs.

[52] US. Cl 72/256, 173/114, 72/284 [51] int. Cl ..B2lc 23/00, B2lc 1/26, B25d 9/00 [50] field of Search 72/285, 284, 467, 256; 173/114 [56] References Cited 7 UNITED STATES PATENTS 3,209,572 10/1965 Boyd 72/285 X 3,209,574 10/1965 Boyd 72/285 X 3,209,573 10/1965 Boyd 72/285 X 3,267,712 8/1966 Atkin 72/467 X 3,342,648 9/1967 Zucker 72/274 X 2,597,500 5/1952 Kerr 72/284 X 3,002,614 10/1961 Jones 72/253 X FORElGN PATENTS 949,555 9/1956 Germany 72/284 Primary ExaminerCharles W. Lanham Assistant Examiner-R. M. Rogers Attorney-Gray, Mase & Dunson ABSTRACT: This invention involves a process and apparatus for deforming metal which consists of applying pressure to the metal surface of a magnitude to effect preselected directional metal flow. The pressure is applied in the form of dual working forces superimposed on one another. One of the working forces consists of a relatively steady continuous force while the other is pulsating. A preferred apparatus of the present invention consists of a die axially mounted relative to an elongated workpiece and free to move a limited distance along this axis. Parallel dual working means, one being disposed to provide a relatively steady working force and one being disposed to provide a pulsating working force are mounted to drive said die over said workpiece or said workpiece through said die. Other embodiments of the present invention include an apparatus and method for stamping and deep drawing sheet or strip metal with a die by utilizing parallel dual steady and pulsating working forces.

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METAL WORKING BACKGROUND and relates in particular to new and novel apparatus and method for forming metals with dies.

In the metalworking industry it has long been the practice to form metals such as metal strip, tubing, wire, rod, etc., by forcing a metal workpiece through the orifice of a closed (continuous wall) die. The die orifice is of smaller dimensions than the workpiece so that the metal is forced to plastically deform and flow into a desired shape. For example, tubing, rod, and wire members are frequently reduced in diameter and elongated by being drawn or extruded through a die having an orifice of lesser diameter than the starting workpiece so that the force required to conduct the metal through the die orifice exceeds the yield strength of the metal thereby resulting in plastic flow. In another such conventional metalworking procedure, strip or sheet metal is forced between male and female die members in a manner to form a deep-drawn container. As in the wire, rod, and tube drawing procedures the metal is subjected to stress beyond its yield point so as to plastically flow and form the container-type deep-drawn part. A still further conventional method for forming metal parts is the extrusion of solid metal billets through the orifice of a die. As in the case of the preceding discussed conventional metalworking methods the yield strength of the workpiece is exceeded so as to cause plastic metal flow through a die orifice of smaller dimensions than the cross-sectional dimensions of the workpiece.

In each of the aforementioned metaLforming operations plastic metal flow is accomplished by a relatively smooth and steady application of pressure of a magnitude to overcome the initial high static frictional forces that exist between the workpiece and the die plus the yield strength of the metal and then the dynamic frictional forces plus the yield strength of the metal in continuing the deforming processes. Such metalforming processes are fairly successful in forming relatively soft and ductile metals such as essentially unalloyed copper, aluminum and iron and many alloys of such metals in their fully annealed or softened condition. However, many metals, are susceptible to strain hardening when subjected to such forming operations at ambient temperatures (below their recrystallization temperatures). Such strain hardening characteristics limit the amount of deformation that can be accomplished without fracture since the hardened material becomes brittle and unpliable. Additionally the residual stress imposed by cold working such materials is frequently an undesirable characteristic causing checking and cracking, particularly in deep-drawn parts.

The solutions to the work-hardening problems conventionally employed are to effect a series of metalworking steps while heat treating the intermediary products. For example, in a given drawing operation a metal workpiece may be given numerous light draws accompanied by one or more intermediary anneals before the desired shape or tolerances are attained. The disadvantages of such multiple forming steps, heat treatments, and accompanying surface conditioning requirements in terms of equipment, costs, and time are self evident.

Another group of metals and alloys that benefit substantially from the method and apparatus of the present invention are the so-called superalloys which exhibit brittle and near brittle properties even when in their fully annealed condition. These materials are frequently mechanically deformed by hot working (working at elevated temperatures usually at or above recrystallization temperatures). Even at their hot working temperatures many of these compositions are highly resistant to deformation and exhibit extensive surface cracking after working (particularly when extruding).

INVENTION We have found that the disadvantages of the prior art form ing techniques are attributable in a large part to the relatively smooth or gradual application of deforming pressures. Our process consists essentially of a cyclic or pulsating working force accompanied by a superimposed relatively steady nonpulsating working force. By employing such a combination of forces we have found it to be possible to more readily deform metals susceptible to cold working without frequent stress relieving heat treatments. By our method and apparatus we have found it to be possible to deform superalloys to a far greater extent and with far greater case than has previously been thought possible. Our method and apparatus has not only proved to be effective for deforming the difficult to deform metals discussed above but has proved to be useful for forming even soft and pliable metals with far greater ease and efiiciency than has previously been thought possible.

In the method of the present invention a relatively steady working force is preferably superimposed on a cyclic or pulsating metalworking force. The cyclic or pulsating working force and the superimposed metalworking force are preferably parallel. The combined forces are of a magnitude to effect metalworking.

The cyclic force of the present invention is distinguished from the prior art technique of applying ultrasonic vibrations during metalworking in that the presently defined force is directional and is of far greater magnitude than a transducer imposed vibration. In the preferred method of the present invention the cyclic or pulsating working force drives the metal workpiece and/or metalworking tool or tools against one another with sufficient force to accelerate metal deformation however, the superimposed steady working force is sufficient to maintain or continue metal flow between the pulsations of the cyclic working force.

The frequency of the pulsating metalworking force is not critical and may be advantageously varied widely from a few strokes per second to ultrasonic frequencies; however, best results are presently attained by employing frequencies of from about 10 strokes per second up to ultrasonic frequency. Such pulsating force will generally be uniform although uniformity is not a prerequisite.

DETAILED DESCRIPTION FIG. 1 is a side elevation view, partially in cross section, of an apparatus that is in conformity with the present invention.

FIG. 2 is a top plan view of the apparatus of FIG. 1.

FIG. 3 (divided into FIGS. 3a and 3b), is a side elevation view, partially in cross section, of a dual point and draw apparatus that embodies the features of the present invention.

FIG. 4 (divided into FIGS. 4a and 4b) is a top plan view, partially in cross section, of the apparatus of FIG. 1.

FIG. 5 is an enlarged cross-sectional view of the die and hammer apparatus of the device of FIGS. 3 and 4 as seen along the line 5-5 of FIG. 4.

FIG. 6 is an elevation view, partially in cross section of a rotatable die modification of the apparatus of FIGS. 3 and 4.

FIG. 7 is an illustrative cross-sectional view of the application of back pressure during extrusion.

FIG. 8 is an elevation view, partially in cross section, of a deep drawing apparatus that embodies elements of the present invention.

FIG. 9 is an elevation view, partially in cross section, of still another deep drawing apparatus that embodies features of the present invention.

FIG. 10 is a perspective view of a metal tubing which has been folded or formed over a metal bolt by means of the method and apparatus of the present invention.

In the apparatus of the drawings, FIGS. 1 and 2 depict a drawbench type of apparatus which consists essentially of a supporting table 10, upright supporting members 12, and spaced guide rods 14 supported therebetween. At one end of the bench or table 10 a hydraulic cylinder 16 is mounted to an upright support 12 so that the plunger 18 is positioned for extension over the table 10 between guide rods 14.

Crossbars 20, 22, 24, and 26 extend between and are slidably engaged with the spaced parallel guide rods 14.

Crossbars and 22 are spaced from and connected to cross bar 24 by spaced parallel frame members 28 to form a yoke assembly 30 in which there is mounted a conventional airhammer 32.

Airhammer 32 is caused to extend through a suitable opening in crossbar 24 and is clamped into position between clamp members 36 and 38, one of which is attached to crossbar 24. Additionally, the handle 40 of airhammer 32 is held to crossbar 22 by means ofa bracket or strap 42 that is bolted to the crossbar 22.

Since the airhammer 32 is of well known conventional construction the operative details of its construction will not be described in this specification.

Plunger T8 of hydraulic cylinder 16 is attached to crossbar 20 which is in turn attached to cross bar 22 so that extension of the plunger will cause yoke 31) to slide along guide rods 14 and propel hammer 32 in the direction of the arrow.

Crossbar 26 is spaced from and attached to crossbar 24 of yoke 30 by means of parallel supporting members 44. A tube straightener and die holder 46 is slidably positioned within a suitable opening within the cross bar 26. A rearwardly positioned anvil portion 43 of the tube holder and die straightener is positioned to extend within the hammer head 50 of airhammer 32. Thus, extension of plunger 18 of hydraulic cylinder 116 will cause cross bar 26 and tube straightener and die holder 46 to move in the direction of the arrow along with yoke 36 and hammer 32.

The die 52 is positioned within a recessed chamber 54 (FIG. 1) formed in the forwardmost end of the tube straightener and die holder 46 so that it is free to slide parallel to its orifice axis rearwardly (toward hammer 32) until it abuts the shoulders 56 formed by the recessed chamber 54 of the tube straightener and die holder 46 and forwardly (in the direction of the arrow) until it abuts a latch 58.

Tube straightener and die holder 46 is composed of two attached parts consisting of the tube straightener section and the die holder section 47.

Latch 58 is pivotally attached to a bolt 60 that extends forwardly from crossbar 26 and is formed with a slot (not shown) at its free end thatwill engage a bolt 62 also extending forwardly of crossbar 26. When in engagement with bolt 62 latch 56 extends over the open end of chamber 54 of tube straightener and die holder 46 to prevent the die from falling from the chamber. By this arrangement the latch may be raised and die 52 conveniently replaced.

The proximity of the hammerhead of airhammer 32 to the tube straightener and die holder 46 is such that when the air hammer is actuated it drives holder 46 and tends to propel die 52 forwardly (in the direction of the arrow) within chamber 54.

A conventional lath chuck 66 is mounted to an upright supporting member forwardly (in the direction of the arrow) of the tube straightener and die holder 46. Chuck 66 is of conventional and well known construction and will not be described in detail in this specification. Chuck 66 is formed with three fingers 68 axially positioned around the chuck opening (not shown). The chuck opening is aligned with an opening (not shown) in the upright supporting member R2 to which the chuck 66 is mounted. A tubular-shaped workpiece 70 is positioned to extend through the opening in the upright supporting member to which chuck 66 is mounted and the chuck itself and into the mouth of die 52. Unlike its lath function the chuck 66 serves as a guide to center the tube 70 in that fingers 68 do not ordinarily grip the tube but are brought into sufficiently close proximity with the surface of the workpiece to prevent snaking or bending of the tube when pressure is applied to the end of the tube by die 52 through the action of ram 16 or hammer 32.

Cross members 72 positioned forwardly of chuck 68 (in the direction of the arrow) support a V-shaped trough 74 that is positioned to receive that portion of the workpiece 70 that extends forwardly of the chuck. Trough 74 is formed with opposing slots 75 along its sides positioned periodically along its length. Slots 75 are disposed to receive and retain a triangularshaped block 76 which acts as a backstop for the workpiece 70. A smaller V-shaped channel 78 is positioned over the workpiece 70 and is clamped into position by clamps 80 mounted periodically along the sides of trough 74. The function of trough 74 and the associated members (V-shaped member 78, clamps 80, etc.) are to restrain the tube and prevent bending or snaking of the workpiece 70 which is driven into die 52 by ram 16 and hammer 32.

In the operation of the apparatus of FIGS. 1 and 2 workpiece 70 is forced through die 52 by pressure brought to bear by the extension of plunger T8 of ram 16 and the resistance offered by block 76 of trough 74 to the tubular-shaped workpiece 70. During such a forming operation airhammer 32 is actuated so that a pulsating forming force tends to drive die 52 forwardly (in the direction of the arrow) over the workpiece 70. Sufficient pressure is applied by ram 16 preferably so that metal flow of tube 70 through the orifice of die 52 continues between pulsations. Thus, the superimposed working forces of the method of the present invention are accomplished.

Where the workpiece 70 is a tube as illustrated by FIGS. 1 and 2 it is preferable that guide means be employed to guide the extruded (reduced) end of the tube emerging from the die orifice. Without such guide means minute deviations in die shape or tube wall may cause the tube to snake" or bend out of alignment with the axis of the die. Tubes or rods worked by the method of the present invention are particularly susceptible to such misalignment since the metal is in a superplastic (extremely ductile) condition as it emerges from the die. Thus, the tube straightener and die holder 46 is provided with a cylindrical chamber 82 extending rearwardly (from the direction of the arrow) from chamber 54. There is positioned within chamber 82 a piston 34 disposed to slide therein. Piston 34 is provided with a forwardly extending axially aligned tube guide rod 86 of a diameter to fit snugly within the [.D. of the tubular-shaped workpiece 70. The extruding end of the tube moving in an opposite direction to the arrow will then engage and project over guide rod 86 and propel piston 34 in front of the extruded tube along chamber 82 assuring axial alignment of the extruded end of tube 70.

To assure proper positioning of piston 84 and insertion of guide rod 86 into the extruded end of workpiece 70, back pressure on the workpiece (forward pressure in relation to the arrow) is provided to piston 84 by means of opposing bolts 88 attached to piston 84 which extend through appropriately positioned slots 90 in the housing of the tube straightener and die holder 46. Springs 92 appropriately attached to crossbar 26 bear on bolts 88 to provide the desired back pressure.

It will be appreciated that the apparatus of FIGS. t and 2 may be readily modified to render it more versatile. The device as shown may be used to point and draw a tube such as workpiece 70. For example, after pointing tube or workpiece 70 (as shown) airhammer 32 and the tube straightener 45 can be removed and conventional tube grippers can be mounted to crossmember 20. By anchoring crossbar 26 and die holder 46 and gripping the extruded end of tube 70 with grippers attached to crossbar 24, the tube can be drawn through die 52 in a conventional manner.

It will be appreciated that metal workpiece 70 can be a solid metal bar or billet as well as a tubular member (omitting the tube-straightening features).

It will also be noted that the axial forces urging die 52 over workpiece 70 are relative. For example, a hydraulic cylinder such as cylinder 16 may be axially positioned on the other end of the bench 10 to urge the workpiece 70 through the die, either independently or cylinder 16 or in combination with the forces applied by cylinder 16. Likewise, a hammer such as hammer 32 could be utilized to hammer workpiece 70 through die 52 either independently of present hammer 32 or in combination with the forces of hammer 32. Also, the cyclic forces of a hammer such as hammer 32 can (as illustrated below by the device of FIGS. 3 and 4) be applied to workpiece 70 during drawing in the manner described above. Thus, it will be apparent that when the term parallel working forces" are utilized in the present specification and claims such term will mean parallel and in the same direction and/or parallel and in reverse directions.

A preferred mode of utilizing the apparatus of FIGS. 1 and 2 is to position workpiece 70, substantially as shown, and extend plunger 18 of cylinder 16 with sufficient force to effect the extrusion without activating hammer 32. Hammer 32 is, however, activated to effect a hammering force of about cycles per second. Without such superimposed parallel hammering force workpiece will not form in a desired manner.

The apparatus of FIGS. 3 and 4 consists of an elongated drawbench type of device. The FIGS. are divided into FIGS. 3a and 3b and 4a and 4b. This apparatus is shown as a dual device having mirror-imaged opposing ends and 100 for the rapid and efficient reduction of elongated workpieces such as is necessary for competitive manufacturing. However, it will be appreciated that either unit 100 or 100' can be effectively utilized as a single unit in the manner of the apparatus of FIGS. 1 and 2. It will also be understood that in accordance with the following description any description of a component or function of the device of end 100 shall have a corresponding component or function of the device of end 100' whether or not such corresponding component or function is identified.

The apparatus of FIGS. 3 and 4 consists'essentially of a platform 111, spaced parallel supporting l beams 110, upright supporting frames 112 and 112 attached to either end of platform 111 and beams and spaced parallel guide rods 114 supported therebetween. Hydraulic rams 116 and 116 (only partially shown) supported by upright supporting frames 112 and 112' respectively are positioned to extend their plungers 118 and 118' toward one another between guide rods 114. Plungers 118 and 118' are threaded at their free ends 120 and 120 and in the view of the figures are threadedly engaged with tube (or bar) grippers 121.

Airhammer assemblies 122 and 122' are mounted to and supported by crossbars 124 and 124' which slidably engage the guide rods 114 so that the extension or retraction of plungers 118 and 118' will cause crossbars 124 and 124' to slide along guide rods 114 in the direction of the arrows or in a reverse direction to cause the hammer assemblies 122 and 122 to be positioned between the guide rods.

There is positioned forwardly (in the direction of the arrows) of crossbars 124 and 124' additional crossbars 128 and 128' which also slidably engage guide rods 114. Die assemblies shown generally at 130 and 130' are centrally mounted to crossbars 128 and 128'.

Die assemblies 130 and 130 are composed of dies 132 and 132' mounted within die holders 134 and 134' that are bolted to crossbars 128 and 128' respectively. Die holders 134 and 134 are disposed to restrain lateral die movement but permit a degree of free axial movement that is limited by restraining shoulders 136 and 136.

Dies 132 and 132 are axially aligned with openings 138 and 138 formed in crossbars 128 and 128 respectively. Bushings 140 and 140' positioned in openings 138 and 138 provide sliding surfaces for hollow bumper members 142 and 142'. Hollow bumper members 142 and 142' are aligned to abut the back surfaces of dies 132 and 132' and are of a configuration and outside diameter to slide within die holders 134 and 134 a distance restricted by the shoulders 144 and 144' respectively.

There is mounted to and extending forwardly of (in the direction of the arrows) upright frame members 112 and 112 two additional hydraulic cylinders 146 and 146' respectively positioned on either side of and spaced from plungers 118 and 118' of rams 116 and 116' respectively. The plungers 148 and 148' of cylinders 146 and 146' extend through passageways 150 and 150 formed in crossbars 124 and 124' and passageways 151 and 151' of crossbars 128 and 128 respectively. Plungers 148 and 148' are attached to these crossbars with positioning nuts for convenient detachment for purposes explained in greater detail herebelow.

A tubular-shaped workpiece 152 is shown to be axially aligned with both dies 132 and 132' and is centrally held within a gripping mechanism 154 which consists of an upright supporting member 156 bolted to the platform 111 and provided with a horizontal flange 158 formed with a groove 160 disposed to receive the workpiece 152. A top plate 162 formed with a corresponding and matching longitudinal groove (not shown) is disposed to cooperate with longitudinal groove 158 in accommodating and gripping workpiece 152 when plate 162 is bolted to flange 158 (as shown).

Airhammer assembly 122 is constructed of a sleeve-shaped work-contacting head portion 166 (FIG. 5) and a sleeveshaped piston section 168 mounted horizontally within a housing 170. Housing 170 consists of sleeve-shaped walls 172 enclosed around head 166 by end ring 174 and rearwardly by the circular flange 176 of a hollow rod 178 extending forwardly through sleeve-shaped piston 168 and into an expanded area 180 of head 166. Piston 168 slides on rod 178 within housing 170 and head 166 slides in and out of housing 170 on bushing 182 that is positioned between ring 174 and head 166. Head 166 is urged rearwardly into housing 170 by a spring 184 which bears on ring 174 and the outside shoulder formed by the expanded area of the head within the housing 170. Piston 168 is urged rearwardly by a spring 186 which surrounds rod 178 and bears on a shoulder 188 formed within the expanded area of head 166. Sealing rings 190 positioned within appropriate circumferential grooves in piston 168 seal the piston from compressed air penetration in respect to housing 170 and rod 178. Port 192 is provided as a compressed air inlet and port 194 is provided as a compressed air outlet.

In the operation of the airhammer compressed air provided to inlet 192 via hose connection 196 FIG. 3) drives the piston 168 forwardly overcoming spring 186 to strike head 166 which, in turn, overcomes spring 184 to strike bumper 142 and drive die 132 over workpiece 152. At the instance piston 168 advances forwardly area 198 is exposed to outlet port 194 and air pressure in back of piston 168 drops so that spring 186 drives piston 168 back to the position shown by FIG. 5. Spring 184 returns head 166 to the position shown. This cycle is repeated as long as a predetermined pressure is maintained in conduit 196. The effect is rapid (20-60 cycles per second) hammer blows on die 132 via bumper 142.

Thus, die 132 may be driven over the workpiece 152 by extending the plungers 148 of cylinders 146 so that positioning nuts 149 engage crossbar 124 and drive the crossbar and hammer assembly 122 into engagement with die assembly 130 and crossbar 128 to advance these members on guide rods 114 in the direction of the arrow. By such means workpiece 152 is extruded through die 132. If airhammer 122 is simultaneously activated by supplying air pressure to conduit 196, the method of the present invention is accomplished.

Since bumper 142, head 166, piston 168, and rod 178 of hammer assembly 122 are hollow, the die 132 and crossbar 128 may be advanced over the tube 152 for an extended distance.

It will be readily noted that a tubular workpiece such as workpiece 152 may be pointed on either end simultaneously to form an automobile axle type of structure by activation of both units 100 and 100' of the device of FIGS. 3 and 4.

Since the hammer assembly 122 is hollow, the extruded or pointed workpiece will extend through the hammer as the die is advanced. Plunger 118 of ram 116 may then be advanced to engage the reduced or pointed end of the workpiece with the jaw 119 of a gripper assembly 121. workpiece 152 may then be released from the gripper assembly 154 and by maintaining plungers 148 extended and by retracting plunger 118 workpiece 152 will be drawn rather than extruded through die 132. This may be a straight-drawing operation or may be accompanied by activation of hammer assembly 122 to simultaneously draw through die 132 and urge die 132 over workpiece 152 witha parallel superimposed cyclic force.

Tube grippers 121 are of conventional design and consist of a hollowed metal block 123 provided with shims 125 and gripper inserts 127 disposed to slide along the surface of shims 125 and grip a tubular member inserted between inserts 127 through a forwardly positioned inlet port 129. Retraction of the tubular member causes inserts 1127 to slide along the surface of shims 1125 and close tightly around the tube.

lt will be noted that in the apparatus of FIGS. 3 and 4 crossbars 1241 and 1123 may be held together on plungers 1148 by adjustment nuts 149. So long as die 132 may move axially within the die holder 1341 and hammerhead 166 may effectively drive bumper 1412 and die 132 a limited axial distance such an arrangement can be effectively employed. Indeed, die assembly 132 and hammer 122 can be easily assembled into a single unit mounted to a single crossbar. Further, a tube straightener and die holder such as holder 16 of the apparatus of FIGS. 1 and 2 can be combined with a hammer assembly such as hammer 122 to form a single unit.

It will be obvious that with the apparatus of FIGS. 3 and 4 one may first point and then draw a workpiece with unit 1110 and then point and draw the same tube with a smaller diameter orifice die with unit 1011 without removing the workpiece from the apparatus. In this manner any number of high reductions may be taken on a single tubular workpiece rapidly and efiiciently without the necessity of removing the workpiece from the apparatus or pointing with a separate device.

A still further modification of the apparatus is illustrated by FIG. 6. In this modification the die 1132 is affixed to a wheel 220 that is rotatably mounted to crosshead 128. The rotational mounting consists of a ball bearing assembly 2119 attached to wheel 220 and seated within a recessed portion of crosshead 128. Such rotation is shown to be effected by a drive chain 222 and sprocket wheel 22 1 that is rotatably mounted to a hollow shaft 226 attached to wheel 220. Thus, die 132 can be caused to rotate when tubular-shaped workpiece 152 is brought into intimate contact with the die. Extension of plunger 1118 (assuming it is attached to hammer assembly 1122) will bring hammer assembly 122 into contact with bumper 1412 and shaft 226 and three forces may be brought to bear on workpiece 152 and these are: (l) the spinning motion of die 132; (2) the hammering action of hammer 122; and (3) a superimposed pressure effected by ram assembly 116 (or cylinders 1416).

An obvious modification of the apparatus of FIG. 6 is to provide an extended end to shaft 226 capable of independent rotation in respect to the rotating shaft for the purpose of providing a nonrotating surface for contact with head 1166 of hammer assembly 1122.

Other obvious modifications too numerous (and redundant) to include in the specification are: (l) mounting more than one die in tandem to crosshead 128 (the multiple hammer blows and superimposed pressure will allow one to perform multiple workpiece reductions without intermediate annealing); (2) rotatably mounting multiple dies in tandem to crosshead 1128 (and rotating them in the same or reverse directions); (3) rotating the workpiece rather than the die or dies; and (4) maintaining the hammer 122 stationary (but activated) and superimposing pressure on the workpiece to propel it into the die.

A difficulty encountered when extruding any elongated member through a die such as a tube, rod, or billet is the tendency of the emerging extrusion (from the die) to form cracks on the extrusion surface. End cracking (cracks appearing on the extruded end of a workpiece) is common. Although such cracking is not so prevalent when utilizing the method and apparatus of the present invention as when using conventional methods and apparatus, we have found that end cracking can be virtually eliminated by the use of back pressure during extrusion. Such back pressure can be any force or pressure that opposes the extruding force or forces. The spring 92 of the tube straightener and die holder 416 of the apparatus of FIGS. 1 and 2 offers some such back pressure to the extruding end of workpiece 761. Although greater back pressure than can be provided by such springs are needed to take practical advantage of this phenomenon, any back pressure or counterforce will have some beneficial effect in reducing the surface cracking or end cracking of extruding members. Such back pressure must, of course, be less than the extrusion force plus the resistance of the metal of the workpiece to extrusion or no extrusion will take place.

FIG. 7 illustrates an application of back pressure to a workpiece 310 as it is expressed through a die 312 by the application of the superimposed working forces applied by a ram 3141 and hollow hammer 316 as through the utilization of the method of the present invention. Back pressure is applied to the extruded end 3111 of workpiece 3110 by means ofa hydraulic cylinder 318. The hydraulic pressure within cylinder 318 is regulated to be overcome by the extruding forces applied by ram 314 and hammer 316 so that extrusion of the workpiece can proceed. We have found that the utilization of such back pressure has enabled us to extrude materials at ambient temperatures never before worked in this manner (i.e., tungsten and cast iron bars).

It will be noted that in the illustrative apparatus of FIG. 7 the billet receptacle 322 is shown as having received the extruded end of billet 3110 after it has passed through the hollow hammer 316. However, it is preferred that back pressure be applied immediately as the extruded end of the billet emerges from the die orifice. Consequently, hollow hammer 316 and bumper 317 preferably will have an inside diameter of sufficient size to accommodate receptacle 322 so that this member can be positioned to apply back pressure immediately as the extrusion emerges from the die.

Receptacle 322 is shaped to receive and confine the extruded end of billet 310.'One embodiment is that receptacle 322 be of a size to cause some forming of the extruded end, however, such forming is not an essential feature of the use of back pressure since in many instances the mere resistance offered by a flat surface is sufficient.

It may be desirable in some instances to provide an end to the plunger of cylinder 318 that may be projected into or through the die to contact the workpiece in advance or during extrusion. Such an end may have a flat surface so that the extruded end of the billet would not be encompassed by a receptacle such as is provided by receptacle 322.

Another advantageous use of back pressure is the application of an end-containing member to the extruded end of the billet workpiece to contain it in a manner to avoid the occurrence and/or propagation or cracks. Such a procedure is advantageous whether or not much actual back pressure is employed. Additionally, it may be desirable to attach a sleeve or twisted wire to the end of a member extruded in accordance with the method of the present invention to minimize such cracking and crack propagation.

The application of such an end containing" member is illustrated in FlG. 7 by a cup-shaped member 3211 positioned within the receptacle 322 formed in the end of the plunger of cylinder 31%. The receptacle 322 is preferably designed to fit tightly over the end of the emerging billet 3110 so that cupshaped member 320 confines the surface of the extruded end of the billet. Some plastic metal flow may occur to either the end of the billet and/or the cup-shaped member 3211 upon the entry of the extruded end of billet 310 into receptacle 322. Cup-shaped member 320 is preferably made of a softer metal than workpiece 310. For example, we may use a copper or red brass cup-shaped member when we are extruding exotic metals such as tungsten.

In place of cup-shaped member 320 we may use a sleeve. Additionally, receptacle 322 and/or cup-shaped member 320 may be flared outwardly to shape the end 311 of workpiece 3110.

Although we have shown the utilization of such back pressure in conjunction with our method and apparatus for extrusion, we have found the utilization of such back pressure to be valuable in minimizing surface and end cracking in any extru sion process including rolling, caming, or swaging processes. in each of these processes an elongated member is forced (pushed) through a metalworking zone and end cracking is prevalent. For the purposes of the present specification and claims all of these processes shall be included in the generic term extrusion where it is used in conjunction with back pressure.

Surface and end cracking are generally attributed to surface stresses imposed by the confinement of the workpiece by the die. We speculate that our use of back pressure tends to counteract such stresses and neutralize their effect.

In addition to reducing the diameter of tubes and billets, the method and apparatus of the present invention may be utilized for the fabrication of laminated tubular structures. For example, we have constructed laminated tubular structures on apparatus such as that depicted by FIGS. 1 and 2 of the drawings by slipping a tube of small O.D. inside of a tube of a larger diameter ID. and by reducing these tubes in the manner described above (relative to tubular workpiece 70) have effected a laminated or bimetallic tubular structure. Further, we

. have effected honeycomb tubular structures by pack reductions of a number of small tubes within a large tube. We have created such bimetallic structures from different materials such as titanium and stainless steel.

Additionally, by the method and apparatus described we find that the die orifice of die 52 (or 132) need not be round but can be square, rectangular, hexagonal, or can, in fact, be of nearly any shape. Appropriate workpieces (generally tubular) can be drawn (or formed) to a variety of cross-sectional shapes by varying the shape of the die orifice. Further, we find it possible to provide fins to a workpiece by creating slots in the die that radiate from the die orifice.

We can also extrude or draw over a mandrel and can shape a tubular workpiece into a variety of cross-sectional configurations by utilizing a mandrel of the desired cross-sectional shapev The die may have a complementary shape or may be fabricated of a soft metal such as red brass that is capable of conforming to the mandrel shape during extrusion or drawing. For example, we have used our method and apparatus to reduce (as by extrusion) a metal tube over the threaded shank of a bolt to forma tube of reduced diameter with a threaded l.D. (See FIG.

Still further, we have found that in addition to the advantages attained by the application of superimposed steady and pulsating forces in extruding or drawing tubular workpieces over a mandrel, we have found it to be advantageous to axially oscillate the mandrel. By such means it is possible to remove the mandrel from the reduced workpiece at the conclusion of extrusion or drawing without the necessity of applying force.

We have found a further advantageous feature of the method of the present when it is employed to extrude or draw metal tubing on a mandrel. In the application of the method of the present invention to forming metals generally we have observed that the metal is more ductile and readily formable immediately after forming than before forming or soon after forming. This appears to be a time related effect so that further forming can be advantageously effected immediately after metal forming (by our process). Where we have extruded or drawn a tube onto a mandrel we find that the workpiece metal remains soft and ductile until soon after the mandrel is removed. This property is significant since it enables one to store extruded (or drawn) tubing in a ductile state (on mandrels) preparatory to subsequent forming.

The apparatus of FIGS. 8 and 9 relate to the application of the method of the present invention to stamping (i.e., coining, blanking, punching, shearing, bending, hot and cold forging, etc.) and deep drawing of metal sheet. The apparatus depicted is a press-type device, however, the exact type of apparatus utilized is optional. The principals of the present invention as they relate to the drawing and stamping of sheet metal may be applied by a drawbench type of apparatus as well as the presstype apparatus of FIGS. 8 and 9.

The apparatus of FIG. 8 consists of a table 410 (supporting structures not shown) upon which there is bolted a die holder 412 formed with a die receiving recess 414 in which there is positioned a female die 416. Table 410 is also provided with an appropriately positioned opening 419 through which a deep drawn part from die 416 may be accommodated. The punch or male die portion 418 is vertically supported by and is mounted to a ram 420 (supporting structures not shown). There is positioned between ram 420 and punch 418 an airhammer assembly 422.

Airhammer assembly 422 may be constructed in a substantially identical manner to airhammer assembly 122 of the apparatus of FIGS. 3 and 4 except, of course, there is no necessity for bumper 166 or rod 176 to be hollow.

The components of the apparatus of FIG. 8 described above are substantially the minimum components for effecting a deep draw while utilizing the method of the present invention. Disregarding the other optional fixtures shown, a workpiece 424 may be positioned over die'416 and punch 418 may be lowered into contact with the workpiece by extending plunger 426 of ram 420. Airhammer 422 is activated to impose cyclic downward pulsations to punch 418. The combined working forces consisting of the pulsating force imposed by hammer 422 and the relatively steady force applied by cylinder 420 will deep draw workpiece 424 through die 416 in a far more efficient manner than has heretofore been known.

Optional but preferred apparatus utilized in conjunction with the apparatus of FIG. 8 include workpiece holddown means which consists of a plate 428 suspended by the plungers 430 of vertically suspended hydraulic cylinders 432. Attached to and depending from plate 428 is a pressure ring 434 which is disposed to contact the surface of the workpiece 424 opposite to (preferably slightly outwardly from) die 416. Preferably pressure ring 434 is of a corresponding shape to die 416. The application of preselected pressure to workpiece 424 by cylinders 432 of a magnitude to hold workpiece 425 in position during the drawing step is needed for accurate alignment of the workpiece due to the pulsating or vibrating effect created by hammer assembly 422.

An additional outwardly positioned pressure ring 436 mounted to plate 428 and positioned opposite a like pressure .ring 438 mounted to plate 412 offers additional stability to the workpiece during drawing. The metal of workpiece 424 flows between the opposing rings 436 and 438 and ring 434 and die 416 providing excessive pressures are not applied by cylinders 432. It will be understood that depending on the exact parameters of the drawing operation (metal being drawn, guage, deepness of draw, etc.) ring 434 alone or rings 438 and 436 may be sufficient.

A further potentially useful modification of the apparatus of FIG. 8 (not shown) is the positioning of an airhammer assembly such as assembly 422 between cylinders 432 and plate 428, By imposing pulsating hammer blows to the opposing rings 436 and 438 and/or ring 434 and die 416 the plastic flow characteristics of workpiece 424 is enhanced.

A still further advance of the method of the present invention is the application of back pressure to a metal workpiece during drawing or extruding. Such back pressure in the utilization of the apparatus of FIG. 8 is accomplished by means of a hydraulic ram 440 vertically mounted beneath the opening 419 of table 410 with its plunger 442 extending upwardly. An anvil 444 mounted on the top of plunger 442 is positioned within the orifice of die 416 to contact the bottom of the drawn part as drawing begins. We have found that if back pressure is offered by ram 440 (of a magnitude that is overcome by the combined forces of ram 420 and hammer 422 the metal of workpiece 424 becomes more plastic and flows between die 416 and punch 418 with greater ease and less residual stress exists after drawing.

A still further advantageous feature of the apparatus of FIG. 8 that is not shown is the positioning of an air hammer between ram 440 and anvil 444. The use of both pulsating and steady pressures as back pressure (overcome by ram 420 and hammer assembly 422) still further enhances the plastic flow of the workpiece.

in h apparatus f 9 table ram hammer AMPCO bronze, Grade 25, and were of a shape approximatey i Punch ram and anvil are of ldenlily that shown by FIG. I. Pointing was accomplished by placing Cal n c i n 1 h appa atus of H0. 7 n r T- dies of progressively smaller l.D.s into a tube straightener and respondingly numbered. The die 446, however, is itself bolted die holder such as tube straightener and die holder 46 of the to table are. Hammer assemblies are mounted on the apparatus of FIGS 1 d 3 The plunger f the ram 16 was p g of hydl'allllc cyllhdel's 449 that are posltlolled around tended to push the die over the tubing while hammer 32 was die The hammer heads 450 are formed to contact the activated. Atypical sequence of the reductions wasasfollows: edges of the workpiece 452. Plastic metal flow and efficient I. 0.846-inch O.D. forming is greatly enhanced when drawing with ram 420 and l 0 2. 0.778-inch O.D. hammer 422 if pulsating hammer forces are applied to the 3. 0.670-inch O.D. workpiece periphery by hammer assemblies 448. As the work- 4. 0.577-inch O.D. piece 652 flows through the orifice of die M6, hammers 44d 5. 0.402-inch CD. are advanced toward the die by extending the plungers of b. Following a substantially identical procedure to that cylinders M9 to maintain contact between hammer heads 450 described in (a) above, 0.20-inch-thi ck wall, Ti-6Al-4Y alloy and the ed f the work ie e, tubing was reduced from 0.625-inch CD. to 0.450-inch. O.D.

lt is preferred that hammer assemblies M8 be paired and There were annealsoppose one another. it is also desirable that at least four such Apparatus Such as that described in conjunction with hammer assemblles be p y lt l5 further desirable that NOS. 1 and 2 was employed to produce threaded tubes as illlalllmel' heads 45ml be elongated 35 to Contact most of the lustrated by FIG. 10 of the drawings. Carbon steel bolts were workpiece g It would also be desirable to provide control inserted into the end of l-inch OD. 304 stainless steel tubing. means synchronously p p i g hammer assemblies 443 Using a series of Grade AMPCO bronze dies the tubing ends towards (lle (lullllg dl'awlllgwere closed over the threaded portion of the bolts. Both lt will be apple-elated that the PP of FlGS- and steady and jackhammer forming forces were employed. imthe methods desel'lhed lh Conjunction Wlth such pp are pressions of the bolt threads were evident on the OD. surface illustrative y and y confine h method of p of the stainless steel tube; however, no springback developed paratus of the present invention to the exact embodiments set in the stainless steel tubing.

forth. The use of superimposed working forces (one pulsating and one steady) is applicable to practically any metalworking operation. For example, the method is applicable to billetpiercing operations where the relative movement of an elongated tool axially pierces a heated billet to produce a tube. Such relative movement of tool and billet may be effected by at least one relatively steady force and at least one pulsating force as in the method of the present invention.

Another example where the method of the present invention is applicable is in hammering or forging operations. instead of the usual heavy hammer blows a steady working force coupled with a pulsating working force (much in the manner of the ram and hammer effect of the apparatus of FIG. 8) will affect hammering and forging in a far more efficient manner than has been heretofore known. A similar and related application of the method of the present invention is in the cold or hot heading and upsetting field. 4 5

A still further application of the method of the present invention is in the field of shearing of metals. Shears such as d. Ms-inch-diameter X 2-inch tungsten rod (RC 40) was extruded utilizing apparatus such as that described in conjunction with FIGS. 1 and 2. Bronze-aluminum alloy dies having approximately the same hardness as the tungsten rod (RC 37-40) were used. The ID. of the die was 0.210 inch. The die was seated in a die receptacle in supporting member 12 in 3 5 place of lath chuck 66 with the die opening facing crossbar 26. The tungsten rod workpiece was mounted in a chucklike holder slidably positioned in crossbar 26 in place of tube straightener and die holder 46. Extrusion of approximately /4 inch of the tungsten rod was accomplished by extending plunger 18 of cylinder 16 so that air hammer 32 engaged the workpiece holder and urged the workpiece into the die. Both the steady pressure of cylinder 16 and the pulsating force of hammer 32 was employed. Back pressure of about 3,000 lbs. was applied by a hydraulic cylinder mounted to crossbars on the other side of supporting member 12 (to the hammer 32).

e. Employing the procedure set forth in ((1) above (except no back pressure was utilized), 0.477-inch-diameter X 2-inch those used for cuttlhg large blllets ale far mole effectlve when Ti-6Al-4V alloy rods were reduced in diameter. Results are a pulsating work force is superimposed on a relatively steady reported i Table shearing force.

TABLE I Diameter Reduction Specimen Die of reduced in area, number Rod material material sectiominch percent Remarks 0. 390 1 0.447-inch diameter Ti-6A1-4V alloy rod (no speci- A1 bronze. 0.335 23 mens available). 0.312 44 This rod was step reduced.

51 2 .do Al bronze 0,390 Three 0.057-inch-high ribs produced on reduced slictignfilby cutting grooves in the die with a an e.

8 Reduction in area calculated based on original rod diameter.

f. employing the procedure set forth in (d) above (except no back pressure was employed) a 1 %-inch length of 0.377-inch The method and pp of the Present lllventlo" has diameter TZM alloy rod was reduced to about 40 percent EXAMPLES been p y to Polllt'. tllblllg P p y to g- A R.A. The specimen was carefully polished to remove all draw bench arrangement Such as that of FlGS- l and 2 was machine marks. Reduction was accomplished in two steps.

used as follows: Aluminum-bronze dies similar in configuration to those shown a. Numerous full hard (RC 40) (drawn), A.l.S.l. Type 304 in the drawings 52 or 132 stainless steel tubes, 0.035-inch gauge wall and 1-inch O.D. g, T concentric tubes of commerciapgrade ll d w r su c f y Pointed t0 5 lnehes) t0 0-402-lnCh titanium were simultaneously reduced through an aluminumwithout intermediary annealing. The dies were constructed of bronze ll di f 8()().i h 0,1) to 0 580 i h 0D,

utilizing the technique described in conjunction with (d) above (except no back pressure). The wall thickness of each tube was 0.060-inch before extruding. A 4-inch length of composite tube was extruded. The composite tube was sectioned, ground through 600 grit, and examined with a 5x hand-magnifying glass. The interface between the two tube walls was not discernible.

h. A section of titanium concentric tubing was reduced over a piece of carbon-steel drill rod using the technique described above to determine if the titanium could be bonded to the steel. The clad rod was sectioned, polished through 600 grit and examined with the hand magnifier. Macroscopically the titanium appeared to be bonded to the steel drill rod. Subsequent metallographic examination of the polished sections showed that mechanical bonding had occurred.

It will be understood that although the apparatus of FIGS. l6 are described in terms of extruding, drawing, and combinations thereof, such apparatus and the method of the present invention are equally applicable to straightening of elongated members. ln many metalworking processes wherein elongated members are produced, such members must be straightened prior to use. For example, in the air frame industry extruded aluminum structural members must be redrawn repeatedly to obtain a reasonably straight product. Such a straightening draw may involve such a slight reduction in cross-sectional area that it is not measurable. However, for the purposes of the present specification and claims, such a straightening operation shall be included within the scope of the claims, particularly those claims directed to drawing.

To illustrate, the application of the method of the present invention to straightening a warped" or slightly bent elongated member would be pointed, threaded through the die 132 of the apparatus of FIG. 4, and gripped by gripper 123. By extending plungers 148 of cylinders 146 and activating hammer 122 drawing or straightening of the workpiece may be accomplished. The advantages of the present invention are as equally applicable to straightening to drawing.

We claim:

l. A method for driving a tool against a metal article comprising applying at least two substantially parallel superimposed directional forces disposed to ui'ge at least portions of said tool and said article toward one another, said forces being of a magnitude to overcome at least a portion of the resistance offered by said article to effect plastic flow of said metal article, at least one of said forces being a relatively steady force and at least one of said forces being a relatively pulsating or intermittent force, and wherein the tool consist of a die, said article consists of an elongated member of greater lateral crosssectional dimensions than the orifice of said die and said forces are disposed to force said article axially through the die orifice.

2. The method of claim 1 wherein said article is a metal tube that is collapsed over a mandrel as it is forced axially through the die orifice.

3. The method of claim 2 wherein said article is shaped by said mandrel.

4. The method of claim 1 wherein said article is a metal tube that is collapsed over one or more tubular members within said tube as it forced axially said die orifice to form bimetallic, laminated, or honeycomb structures.

5. The method of claim 1 wherein the orifice of said die is provided with one or more radial slots so that metal from the walls of said elongated member will flow into said slot as it is forced through said die orifice to form one or more radial fins or flutes.

6. The method of claim 1 wherein said mandrel is oscillated axially in relation to said tube as said tube is collapsed over the mandrels surface.

7. The method of claim 1 wherein said article consists of wire, tubing, rods, or billets.

8. The method of claim I wherein said tool consists ofa die, said article consists of sheet or strip metal, and said forces are dissosed to stam or deep draw said sheet or strip metal.

. The metho of claim 1 wherein said elongated member is partially extruded through said die by said forces and the extruded end is then pulled so as to draw the remaining portion of said member through said die.

10. The method of claim I wherein said elongated member is extruded through said die by said forces and pressure of less magnitude than said metalworking forces is applied to the extruding end of said article emerging from said die, said pressure substantially opposing said working forces.

11. The method of claim 10 wherein the end of said article first to be expressed through said die is encased in a metal sheeting as it emerges from said die so as to prevent cracking.

12. The method of claim 1 wherein said die is caused to rotate while said forces force said article through the die orifree.

13. The method of claim 1 wherein said article is caused to rotate by force through the die orifice.

14. The method of claim 1 wherein a plurality of at least two dies are positioned in tandem and said forces are disposed to drive said article through the multiple orifices of said plurality of dies.

15. The method of claim 14 wherein one or more of said plurality of said dies are independently rotated.

16. The method of claim 1 wherein the magnitude of said relatively steady forces are sufficient to cause said article to plastically flow through said orifice between the intennittent or pulsating forces of said intermittent or pulsating work forces.

17. The method of claim 16 wherein said intermittent or pulsating forces are within the range of from about 2 cycles per second to ultrasonic frequency. 

2. The method of claim 1 wherein said article is a metal tube that is collapsed over a mandrel as it is forced axially through the die orifice.
 3. The method of claim 2 wherein said article is shaped by said mandrel.
 4. The method of claim 1 wherein said article is a metal tube that is collapsed over one or more tubular members within said tube as it forced axially said die orifice to form bimetallic, laminated, or honeycomb structures.
 5. The method of claim 1 wherein the orifice of said die is provided with one or more radial slots so that metal from the walls of said elongated member will flow into said slot as it is forced through said die orifice to form one or more radial fins or flutes.
 6. The method of claim 1 wherein said mandrel is oscillated axially in relation to said tube as said tube is collapsed over the mandrel''s surface.
 7. The method of claim 1 wherein said article consists of wire, tubing, rods, or billets.
 8. The method of claim 1 wherein said tool consists of a die, said article consists of sheet or strip metal, and said forces are disposed to stamp or deep draw said sheet or strip metal.
 9. The method of claim 1 wherein said elongated member is partially extruded through said die by said forces and the extruded end is then pulled so as to draw the remaining portion of said member through said die.
 10. The method of claim 1 wherein said elongated member is extruded through said die by said forces and pressure of less magnitude than said metalworking forces is applied to the extruding end of said article emerging from said die, said pressure substantially opposing said working forces.
 11. The method of claim 10 wherein the end of said article first to be expressed through said die is encased in a metal sheeting as it emerges from said die so as to prevent cracking.
 12. The method of claim 1 wherein said die is caused to rotate while said forces force said article through the die orifice.
 13. The method of claim 1 wherein said article is caused to rotate by force through the die orifice.
 14. The method of claim 1 wherein a plurality of at least two dies are positioned in tandem and said forces are disposed to drive said article through the multiple orifices of said plurality of dies.
 15. The method of claim 14 wherein one or more of said plurality of said dies are independently rotated.
 16. The method of claim 1 wherein the magnitude of said relatively steady forces are sufficient to cause said article to plastically flow through said orifice between the intermittent or pulsating forces of said intermittent or pulsating work forces.
 17. The method of claim 16 wherein said intermittent or pulsating forces are within the range of from about 2 cycles per second to ultrasonic Frequency. 